Progressive optic atrophy associated with excavation of optic nerve head is a hallmark of glaucoma that leads to visual field defects. Although increased intraocular pressure is an obvious risk factor, the mechanisms that lead to the damage of the optic nerve head is still a controversial issue, because glaucomatous optic nerve damage may develop at any level of intraocular pressure. In the past Circulatory or vascular alterations have been considered as a risk factor accounting for the development of glaucomatous optic nerve damage. Fluorescein angiography (FAG) has shown filling defects in the optic disc of eyes with NTG. Color Doppler imaging (CDI) has demonstrated an increase in resistive index (RI) of the ophthalmic arteries in eyes with glaucoma. Laser Doppler analysis showed a decrease in retinal and optic nerve flow in glaucoma patients. Further, measurements of pulsatile ocular blood flow (POBF) showed the POBF to be significantly lower in NTG eyes with or without field loss than in normal subjects.